Floating cover for a storage tank

ABSTRACT

The disclosure herein describes a floating cover which comprises a generally circular planar platform formed of a plurality of concentric groups of interconnected panels made of cellular foam plastics, the panels being identically shaped in the form of an isosceles triangle, each panel including, along one side, a male engaging profile and, along the other side, a female engaging profile, both profiles having correspondingly shaped crosssections whereby adjacent panels may be interconnected in sideby-side relation to form a concentric group; the base of each panel is also provide with an inter-engaging profile to connect the bases of panels of one concentric group with the bases of panels of a radially adjacent concentric group.

United States Patent [191 Szasz Oct. 7, 1975 [73] Assignee: Edmund Sandborn, Westmount,

Canada; a part interest 22 Filed: Aug. 26, 1974 21 Appl. No.: 500,687

Related U.S. Application Data [63] Continuation-impart of Ser. No. 298,430, Dec. 1

1972, abandoned.

3,445,970 5/1969 Nelson 52/82 FOREIGN PATENTS OR APPLICATIONS 890,422 2/1962 United Kingdom 220/216 OTHER PUBLICATIONS Popular Mechanics, Vol. 111, No. 3, Mar. 1959, p.

274, Floating Roof Roof in Tank Reduces Vapor Losses.

Primary Examiner-William I. Price Assistant Examiner-Stephen Marcus Attorney, Agent, or FirmLarson, Taylor and Hinds [52] U.S. Cl. 220/226; 220/216; 220/220 [51] Int. Cl. B65D 87/20 ABSTRACT [58] Field of Search 220/2I6227; The disclosure herein describes a floating cover which 4/l74.12, 174.13, 174.14; 52/3, 5, 81, 82; comprises a generally circular planar platform formed 61/5, 1 F of a plurality of concentric groups of interconnected panels made of cellular foam plastics, the panels being [56] References Cited identically shaped in the form of an isosceles triangle, UNITED STATES PATENTS each panel including, along one side, a male engaging 1,213,592 l/1917 Crawford 52/3 x Profile along the other side femflle engaging 1,229,040 6/1917 Crawford 52/3 profile, both profiles havlng correspondingly shaped 2,193,484 311940 Jones 220/219 cross-Sections whereby adjacent Panels y be inter- 2,464,786 3/1949 Allen 220/219 connected in side-by-side relation to form a concen- 2,635,782 4/ 1953 Orr 220/219 tric group; the base of each panel is also provide with 2,873,042 2/1959 FIDO... 220/222 an inter--engaging profile to connect the'bases of panels of one concentric group with the bases of panels of 3:029:971 4/1962 Reynolds 220 213 a many adjacent concentr'c group 3,296,755 H1967 Chisholm 52/3 6 Claims, 7 Drawing Figures /6 '44,#5#$$I\N JA'A'AYAVAVA\:

US, Patent 0m; 7,1975 Sheet 1 of2 3,910,452

U.S. Patent Oct. 7,1975 Sheet 2 of2 3,910,452

VII. VIII'IA 1 FLOATING COVER FOR A STORAGE TANK This application is a continuation-in-part of patent application Ser. No. 298,430, filed Dec. 1, 1972, now abandoned.

FIELD OF THE INVENTION The present invention relates to a floating cover for liquid storage tanks and, more particularly, relates to improvements in floating seals of the type supported upon the surface of volatile hydrocarbon liquids contained within bulk storage tanks.

BACKGROUND OF THE INVENTION The lost of valuable hydrocarbons to atmosphere as a result of surface evaporation due to differential vapor pressures and solar heat are of considerable economic importance and constitute a significant percentage of atmospheric pollution and smog.

In an effort to control this wastage, efforts have been made to introduce floating seals which are generally of metallic construction utilizing either steel or aluminum fabrications supported upon floats which may be foam filled as a precaution against puncture. The field assembly and installation of such floating seal is very costly, particularly when required to be installed in an existing tank. In addition, troubles are experienced in the operation of such floating seals. In particular, they represent a hazard from static electricity which has to be neutralized by extensive bonding and earthing devices. The mechanical integrity must be perfect and buoyancy may be lost through a single started fastening. This integrity has also been known to be breached by electrolytic corrosion along the joints. The weight of such a floating seal is very considerable and supporting legs have become deformed due to unequal loading imposed by the lack of flatness in the tank bottom. The rectification of such defects is very costly since the tank must first be drained and purged, and the lost of use during repair represents a further costly loss.

OBJECTS OF THIS INVENTION It is an object of the present invention to eliminate these objections and hazards while introducing considerable economies, particularly in the cost of on-site installations.

It is a further object of the present invention to provide a monolithic unit panel in the shape of an isosceles triangle such that plurality of identical units may be easily assembled together to form a planar platform of a generally circular shape.

It is still a further object of this invention to provide a plurality of such panels, made entirely of cellular foam plastics, wherein no metallic components or fastenings are used for interconnecting the panels.

STATEMENT OF THE INVENTION The present invention therefore relates to a floating cover for liquid storage tanks which comprises: a generally circular planar platform formed of a plurality of concentric groups of interconnected panels made of cellular foam plastics, the panels being identically shaped in the form of an isosceles triangle, each panel including, along one side, a male engaging profile and, along the other side, a female engaging profile, both profiles having correspondingly shaped cross-sections whereby adjacent panels may be interconnected in side-by-side relation to form a concentric group of panels; inter-engaging profile means are provided on the base of each panel to connect the bases of panels of one concentric group with the bases of panels of a radially adjacent concentric group.

In the preferred form of the invention, the bases forming the periphery of the circular platform includes end panels equipped with sealing means to provide an air-tight engagement with the inner wall of the storage tank. 7

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description, while indicating a preferred embodiment of the invention, is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a storage tank with a broken wall to show the'floating cover therein made in accordance to the present invention;

FIG. 2 is a perspective enlarged view of two panels used in the platform of the present invention;

FIG. 3 is a schematic representation of a quarter of a platform having six concentric groups of panels;

FIG. 4 is a cross-sectional view taken along lines 44 of FIG. 3;

FIG. 5 is a cross-sectional view taken along lines 55 of FIG. 3;

FIG. 6 is a cross-sectional view taken along lines 6-6 of FIG. 3; 7

FIG. 7 is a cross-sectional view taken along lines 77 of FIG. 3. v

Referring now more particularly to FIG. I, the numeral 10 generally designates a storage tank having a cylindrical vertical wall 12, a bottom 14 and a roof 15. Inside tank 10 a floating cover 16 constructed in accordance with an embodiment of the present invention is shown supported on legs 17 (no fluid being shown in the tank).

The floating cover 16 consists of a generally circular planar platform formed of a series of concentric groups (six being shown in FIG. 3 as 20a, 20b, 20c, 20d, 20e, 20f) of interconnected panels 22, such as shown in FIG. 2.

These panels 22 are preferably moulded from a rigid hard skinned polyurethane closed cell foamed material of low cubic density and possessing fire resistant and self-extinguishing properties. Such material is inert to carbon-hydrate solvents and can be used in direct contact with the fluid upon which it floats while possessing adequate mechanical strength combined with a surface hardness adequate to be used as a working platform.

The circumference of the assembled platform is of a diameter slightly less than that of the internal diameter of the tank wall 12, such that a clearance is left which allows the platform to move with the fluid level without coming into contact with the tank wall; this also allows for a lack of circularity on the part of the cylindrical wall. This clearance between wall and platform is closed, however, by an elastomeric sealing member 26, which is attached to the periphery of the floating platform 16 as hereinafter explained.

The panels 22 are identically shaped in the form of an isosceles triangle with two equal sides 28 and ,30 and a base 32. The panels may be planar or include reinforcing ridges 33 such shown in FIGS. 2 and 4.

To form the first concentric group 20a, a series of these pre-fabricated panels 22 are inter-connected in side-by-side relation. This is accomplished by providing, along one side of a panel, a female engaging profile, such as tongue 34 and, along the other side of the panel, a female engaging profile, such groove 36. This first concentric group of panels is assembled so that it may freely slide along a column 24, which serves to support the roof of the tank. One way is illustrated in FIG. 5 and consists in attaching to the apex of each panel aeircular member 38, made of similar plastic material, to which is attached by means of suitable securing means 40, a sealing canvas 42 of neoprene or urethane, to thereby provide an air-tight engagement with column 24.

The second concentric group 2019 of the platform is formed in a similar fashion by interconnecting panels 22' in side-by-side relation (see FIG. 4). However, this second group b of panels is attached to the first group 200 of panels by their bases 32 which also include inter-engaging profiles which may beofa tongueand-groove arrangement 41-43, similar to the one described above for the side-by-side engagement of panels. The inter-engagement of the bases could also be accomplished by a tongue and groove profile in each base, longitudinally thereof, whereby the base engagement of the panels could be carried out by merely in, verting one panel relative to an adjacent one.

Concentric groups 20c, 20d, 2()e and 20f are assembled and interconnected in a similar fashion.

The tongue and groove profiles are preferably shaped to provide an air-tight engagement once they are locked to one another. FIG. 7 exemplifies one way which consists in providing the profiles Withfurther flange portions 411: and 46a. In another embodiment, the profiles could be further secured with a suitable adhesive.

One important characteristic of the present invention is that the panels may be assembled one to the other within the tank. The geometry of the panels takes the form of a triangle isosceles of such a size that any given plurality of panels may be assembled together to produce a generally circular platform of given size inside the tank. One preferred size of a panel 22 is a triangle with a 16 inches base and with 4 feet 8 inches sides. The dimension of the base of the right triangle is such that it will pass through a standard 24 inch diam. circular access manhole of a tank thereby enabling all the material necessary to complete the floating cover for any size of tank to be introduced through the standard manhole of any approved A.P.I. (American Petroleum Institute) tank.

The platform lfurther includes a plurality of end panels 44 which are made of the same plastic material as panel 22 and which are provided with profile means 46 to correspondingly engage the profile 41 of the base on each panel. As can be seen in FIG. 3, the end panel 44 is adapted to receive the bases of six panels.

The sealing member 26 is formed of foam plastic ma-. terial 48 enclosed within a nylon coated cover 50. This sealing member has a portion fixedly attached (not shown) to the end of the platform, which portion extends over the bases of panels 22 and the end panels 44.

The panels may be shaped to accommodate the supporting legs 17; recesses 52' may be provided in the ridges, 33 to receive the upper part of the legs 17. With the type of plastic material used, it is possible to cut through the panel at recesses 52 whereby the platform may be vertically adjusted relative to the legs 17. FIG. 3 shows a manhole 54 which may be provided on the platform to allow equipment, instruments, or the like to through the platform.

to form aconcentric group; inter-engaging profile.

means on said bases to connect the bases of panels of one concentric group'with the bases of panels of a radially adjacent concentric group. a

2. In a floating cover as defined in claim 1, further comprising end panels eireumferentially disposed on said platform, said end panels havingprofiles for correspondingly engaging the inter-engaging profile means of the bases of the outmost radially disposed concentric group of panels.

3., In a floating cover as defined in claim 1, wherein said panels are moulded from a rigid hard skinned polyurethene closed cell foamed material from low cubic density.

4. In a floating cover as defined in claim 2, sealing. means disposed circumferentially on said end panels for providing an airtight engagement between the platform and a storage tank wall.

5. Ina floating cover as defined in claim 1, wherein each said panel includes reinforcing ridges on one surface thereof.

6. In a floating cover as defined in claim 5, further comprising recessed holes in said ridges to receive supporting legs for said platform.

l l i l 

1. In a floating cover for a liquid storage tank, a generally circular planar platform formed of a plurality of concentric groups of interconnected panels made of cellular foam plastics, said panels being identically shaped in the form of an isosceles triangle with two equal sides and a base; each said panel including, along one side, a male engaging profile and, along the other side, a female engaging profile, said profiles having correspondingly shaped cross-sections whereby adjacent panels may be interconnected in side-by-side relation to form a concentric group; inter-engaging profile means on said bases to connect the bases of panels of one concentric group with the bases of panels of a radially adjacent concentric group.
 2. In a floating cover as defined in claim 1, further comprising end panels circumferentially disposed on said platform, said end panels having profiles for correspondingly engaging the inter-engaging profile means of the bases of the outmost radially disposed concentric group of panels.
 3. In a floating cover as defined in claim 1, wherein said panels are moulded from a rigid hard skinned polyurethene closed cell foamed material from low cubic density.
 4. In a floating cover as defined in claim 2, sealing means disposed circumferentially on said end panels for providing an airtight engagement between the platform and a storage tank wall.
 5. In a floating cover as defined in claim 1, wherein each said panel includes reinforcing ridges on one surface thereof.
 6. In a floating cover as defined in claim 5, further comprising recessed holes in said ridges to receive supporting legs for said platform. 